Gas turbine transition duct with late lean injection having reduced combustion residence time

ABSTRACT

An improved combustion system having a reduced combustion residence time in a combustion turbine engine is provided. The combustor system may include a flow-accelerating structure ( 16, 51 ) having an inlet ( 26 ) and an outlet ( 28 ). The inlet of the flow-accelerating structure is fluidly coupled to receive a flow of combustion gases from a combustor outlet. At least one fuel injector ( 32, 64, 66 ) is disposed between the inlet and the outlet of the flow-accelerating structure. The flow-accelerating structure causes an increasing speed to the flow of combustion gases, and, as a result, the flow of combustion gases in the flow-accelerating structure experiences a decreased static temperature and a reduced combustion residence time, each of which is effective to reduce NOx emissions at the high firing temperatures of the turbine engine.

BACKGROUND 1. Field

Disclosed embodiments are generally related to combustion turbine engines, such as gas turbine engines and, more particularly, to a combustion system having a reduced combustion residence time.

2. Description of the Related Art

In gas turbine engines, fuel is delivered from a fuel source to a combustion section where the fuel is mixed with air and ignited to generate hot combustion products that define working gases. The working gases are directed to a turbine section where they effect rotation of a turbine rotor. It is known that production of NOx emissions from the burning fuel in the combustion section may be reduced by providing a portion of the fuel to be ignited downstream from a main combustion zone. This approach is referred to in the art as a distributed combustion system (DCS). See, for example, U.S. Pat. Nos. 8,375,726 and 8,752,386.

It is also known that certain ducting arrangements in a gas turbine engine may be configured to appropriately align the flow of working gases, so that, for example, such flow alignment may be tailored to avoid the need of a first stage of flow-directing vanes in the turbine section of the engine. See for example U.S. Pat. Nos. 7,721,547 and 8,276,389. Each of the above-listed patents is herein incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary schematic representation of one non-limiting embodiment of a ducting arrangement with fuel injectors disposed at a location in a flow-accelerating structure, such as a flow-accelerating cone, characterized by a relatively lower static temperature and a reduced combustion residence time, each of which is conducive to reduce NOx emissions at the high firing temperatures of a combustion turbine engine.

FIG. 2 illustrate non-limiting plots of decreasing static temperatures as a function of increasing flow speed between the cone inlet and the cone outlet in the flow-accelerating cone shown in FIG. 1.

FIGS. 3 and 4 illustrate further non-limiting embodiments of ducting arrangements with fuel injectors disposed at respective flow-accelerating cones.

FIG. 5 is a schematic of a Ili& injector, which in one non-limiting embodiment may be arranged to provide jet in cross-flow injection,

FIG. 6 is a schematic of a fuel injector, which in another non-limiting embodiment may be arranged without providing jet in cross-flow injection

DETAILED DESCRIPTION

The inventors of the present invention have recognized synergies that result from an innovative integration of what up to the present invention have been perceived as seemingly independent combustor design approaches, such as may involve a distributed combustion system (DCS) approach, and an advanced ducting approach in the combustor system of a combustion turbine engine, such as a gas turbine engine. With the integration of these design approaches, in certain non-limiting embodiments, it is now feasible to achieve a decreased static temperature and a reduced combustion residence time, each of which is conducive to reduce NOx emissions to be within acceptable levels at turbine inlet temperatures of approximately 1700° C. (3200° F.) and above.

In the following detailed description, various specific details are set forth in order to provide a thorough understanding of such embodiments. However, those skilled in the art will understand that embodiments of the present invention may be practiced without these specific details, that the present invention is not limited to the depicted embodiments, and that the present invention may be practiced in a variety of alternative embodiments. In other instances, methods, procedures, and components, which would be well-understood by one skilled in the art have not been described in detail to avoid unnecessary and burdensome explanation.

Furthermore, various operations may be described as multiple discrete steps performed in a manner that is helpful for understanding embodiments of the present invention. However, the order of description should not be construed as to imply that these operations need be performed in the order they are presented, nor that they are even order dependent, unless otherwise indicated. Moreover, repeated usage of the phrase “in one embodiment” does not necessarily refer to the same embodiment, although it may. It is noted that disclosed embodiments need not be construed as mutually exclusive embodiments, since aspects of such disclosed embodiments may be appropriately combined by one skilled in the art depending on the needs of a given application.

The terms “comprising”, “including”, “having”, and the like, as used in the present application, are intended to be synonymous unless otherwise indicated. Lastly, as used herein, the phrases “configured to” or “arranged to” embrace the concept that the feature preceding the phrases “configured to” or “arranged to” is intentionally and specifically designed or made to act or function in a specific way and should not be construed to mean that the feature just has a capability or suitability to act or function in the specified way, unless so indicated.

FIG. 1 is a fragmentary schematic representation of an advanced ducting arrangement 10 in one non-limiting embodiment of a combustor system of a combustion turbine engine, such as a gas turbine engine. In advanced ducting arrangement 10, a plurality of flow paths 12 blends smoothly into a single, annular chamber 14. In one non-limiting embodiment, each flow path 12 may be configured to deliver combustion gases formed in a respective combustor to a turbine section of the engine without a need of a first stage of flow-directing vanes in the turbine section of the engine.

In one non-limiting embodiment, each flow path 12 includes a cone 16 and an integrated exit piece (IEP) 18. In one non-limiting embodiment, each cone 16 has a cone inlet 26 having a circular cross section and configured to receive the combustion gases from a combustor outlet (not shown). The cross-sectional profile of cone 16 narrows toward a cone outlet 28 that is associated with an IEP inlet 30 in fluid communication with each other.

Based on the narrowing cross-sectional profile of cone 16, as the flow travels from cone inlet 26 to cone outlet 28, the flow of combustion gases is accelerated to a relatively high subsonic Mach (M) number, such as without limitation may comprise a range from approximately 0.3 M to approximately a 0.8 M, and thus cone 16 may be generally conceptualized as a non-limiting embodiment of a flow-accelerating structure. Accordingly, the combustion gases may flow through cone 16 with an increasing flow speed, and as a result, this flow of combustion gases can experience a decreasing static temperature in cone 16.

For example, see FIG. 2 that illustrates a non-limiting plot 40 of decreasing static temperature as a function of increasing flow speed between the cone inlet and the cone outlet in cone 16, as illustrated in FIG. 1. By way of comparison, FIG. 2 further illustrates a plot 42 of total temperature, which is essentially independent of the increasing flow speed between the cone inlet and the cone outlet.

The inventors of the present invention have cleverly recognized that by injecting fuel and air at locations of the cone having a relatively lower static temperature, such as a location between cone inlet 26 and cone outlet 28, it is feasible to effectively bring the reaction temperature below the NOx formation threshold even though, in certain non-limiting embodiments, the firing temperature may be approximately 1700° C. and higher. That is, the injector location is in a location where the static temperature is lower compared to the static temperature at cone inlet 26. For the sake of simplicity of illustration, FIG. 1 illustrates a single injector 32, as may comprise an assembly of an air scoop and a fuel nozzle, in connection with each of the cones illustrated in FIG. 1; it will be appreciated, however, that multiple injectors may be circumferentially distributed in each cone 16.

FIG. 3 illustrates another non-limiting embodiment of a ducting arrangement 50 where a flow-accelerating cone 51 may be made up of two or more interconnected cone sections, in lieu of a single-piece flow-accelerating cone, as described above. In one non-limiting embodiment, a first cone section 52 may be arranged to receive the combustion gases from a combustor outlet 54, and a second. cone section 56, affixed at one end to first cone section 52, may be arranged to supply the combustion gases to a corresponding IEP inlet 58. In one non-limiting embodiment, cone sections 52, 54 may each include a respective flattened portion 60 defining a non-varying cross sectional profile where the injectors 32 may be located.

As illustrated in FIG. 4, in one non-limiting embodiment, a respective manifold 34 (e.g., a ring manifold) is fluidly coupled to the fuel injectors 32. In one non-limiting embodiment, manifold 34 may be affixed (e.g., bolted) between respective interconnecting flanges 33, 35. It will be appreciated that aspects of the present invention are not limited to any specific configuration regarding the mechanical design of the flow-accelerating cone; or regarding mechanical arrangements for affixing the fuel injectors to the flow-accelerating cone since such mechanical design and/or arrangements can be readily tailored based on the needs of a given application.

Returning to FIG. 2, one can appreciate a further non-limiting plot 44 of static temperature as a function of flow speed between the cone inlet and the cone outlet in the context of flow-accelerating cone 51, as shown in FIG. 3. A portion 46 of plot 44 corresponds to flattened portion 60 of cone 51, where, although the flow speed may be constant over flattened portion 60, such flow speed would be lower compared to the static temperature at cone inlet 26.

It will be appreciated that in one non-limiting embodiment injectors 64 may be disposed to provide jet in cross-flow injection, as schematically illustrated in FIG. 5, Alternatively, injectors 66 may be positioned normal to a wall 62 of the flow-accelerating cone, as schematically illustrated in FIG. 6, where arrow 68 schematically represents flow direction. It will be appreciated that one can use injector angles relative to the flow direction other than those illustrated in FIGS. 5 and 6, and thus aspects of the present invention are not limited to injector angles normal to the flow or normal to the wall. That is, aspects of the present invention are not limited to any particular modality of injectors or to any particular injector angle relative to the flow direction.

In operation, disclosed embodiments are expected to be conducive to a combustion system capable of realizing approximately a 65% combined cycle efficiency or greater in a gas turbine engine. Disclosed embodiments are also expected to realize a combustion system capable of maintaining stable operation at turbine inlet temperatures of approximately 1700° C. and higher while maintaining a relatively low level of NOx emissions, and acceptable temperatures in components of the engine without an increase in cooling air consumption.

While embodiments of the present disclosure have been disclosed in exemplary forms, it will he apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents, as set forth in the following claims. 

1-20. (canceled)
 21. A combustion system comprising: a flow-accelerating structure defining a flow-accelerating cone between an inlet and an outlet of the flow-accelerating structure, the inlet of the flow-accelerating structure fluidly coupled to receive a flow of combustion gases from a combustor outlet; and at least one fuel injector disposed between the inlet and the outlet of the flow-accelerating structure, wherein the flow-accelerating structure causes an increasing speed to the flow of combustion gases, and, as a result, the flow of combustion gases in the flow-accelerating structure experiences a decreased static temperature and a reduced combustion residence time, wherein a circular cross-sectional profile of the flow-accelerating cone narrows in diameter as the flow of combustion gases travels between inlet and outlet.
 22. The combustion system of claim 21, wherein the flow-accelerating structure comprises a single-piece flow-accelerating cone.
 23. The combustion system of claim 21, wherein the flow-accelerating cone comprises two interconnected cone sections.
 24. The combustion system of claim 23, wherein a portion of the two interconnected cone sections comprises a non-varying cross-sectional profile.
 25. The combustion system of claim 24, wherein said at least one fuel injector is disposed in the portion having the non-varying cross-sectional profile.
 26. The combustion system of claim 21, wherein said at least one fuel injector is arranged to provide jet in cross-flow injection.
 27. The combustion system of claim 21, wherein said at least one fuel injector is arranged without providing jet in cross-flow injection.
 28. The combustion system of claim 21, wherein the outlet of the flow-accelerating structure is fluidly coupled to supply the flow of combustion gases to a turbine section of a turbine engine.
 29. The combustion system of claim 28, wherein the flow-accelerating structure is part of a ducting arrangement configured to supply the flow of combustion gases to the turbine section of a turbine engine without a first stage of flow-directing vanes in the turbine section of the turbine engine.
 30. A gas turbine engine comprising: a combustion system comprising a ducting arrangement having a plurality of flow paths, each flow path arranged to receive a flow of combustion gases from a combustor outlet and to supply the flow of combustion gases to a turbine section of the gas turbine engine; each flow path comprising a flow-accelerating structure defining a flow-accelerating cone between an inlet and an outlet of the flow-accelerating structure, the inlet of the flow-accelerating structure fluidly coupled to receive the flow of combustion gases from the combustor outlet; and at least one fuel injector disposed between the inlet and the outlet of the flow-accelerating structure, wherein the flow-accelerating structure causes an increasing speed to the flow of combustion gases, and, as a result, the flow of combustion gases in the flow-accelerating structure experiences a decreased static temperature and a reduced combustion residence time in the flow paths, wherein a circular cross-sectional profile of the flow-accelerating cone narrows in diameter as the flow of combustion gases travels between inlet and outlet.
 31. The gas turbine engine of claim 30, wherein the flow-accelerating structure comprises a single-piece cone.
 32. The gas turbine engine of claim 30, wherein the flow-accelerating cone comprises two interconnected cone sections.
 33. The gas turbine engine of claim 32, wherein a portion of the two interconnected cone sections comprises a non-varying cross-sectional profile, and further wherein said at least one fuel injector is disposed in the portion having the non-varying cross-sectional profile.
 34. The gas turbine engine of claim 30, wherein said at least one fuel injector is arranged to provide jet in cross-flow injection.
 35. The gas turbine engine of claim 30, wherein said at least one fuel injector is arranged without having to provide jet in cross-flow injection.
 36. The gas turbine engine of claim 30, wherein the ducting arrangement is configured to supply the flow of combustion gases to the turbine section of the turbine engine without a first stage of flow-directing vanes. 